I can’t say with 100 % certainty, but GHB is not covered in the tests provided by the major AUstralian suppliers to industry and law enforcement. It is also not included in the Australian Standards.
I don’t know of anywhere in the world that tests for GHB except for in an autopsy / cause of death situation. Even in those scenarios I think it is undetectable within a very short period 24-48 hours? Don’t quote me on that but I think that’s right